4 point Z probing with heighmap calibration

treetopped

Hi,

I am using Creality coated glass bed, 330x330 mm (Ender 5 Plus).
It is great in many ways, but not especially flat, probably due to additional coating.
The maximum deviation is -0,14 / 0,07, works fine with mesh compensation, very poorly without. And my mesh is 240 points (15 x 16) , which takes a lot of time.

From time to time I need to re-calibrate, usually there is some skew probably related to dualZ, maybe one stepper moves slightly while the printer is off.

But the bed is generally the same all the time, only slightly tilted, so why to probe it again and again?

If after homing Z axis we check four key points, preferably near leveling screws, it should be possible to calculate temporary height map for each print? It would be fast and precise, and could be easily a start of every print.

BTW, how can I check these four key points offset without running mesh compensation and overwriting existing heightmap.csv?

My current workflow looks like this:

1 mesh compensation with four points (near the screws), read the Z offsets, manually readjust the bed, repeat until all offsets are around 0,010, usually takes three to four passes
2 run full mesh calibration, 240 points, mainly because it is overwritten during first step

Maybe I could make my manual correction a little more precisely and retain original height map for a little longer.

Phaedrux

If the mesh itself doesn't change much once the tilt is resolved, you could just load the saved heightmap rather than re-doing the mesh. G29 S1.

If you want to save a mesh to a new file without overwriting the default, you can specify a file name.

See the detailed usage of G29 here: https://docs.duet3d.com/en/User_manual/Reference/Gcodes#g29-mesh-bed-probe

If your dual Z motors each have their own driver, you could automate the tilt correction: https://docs.duet3d.com/en/User_manual/Connecting_hardware/Z_probe_auto_levelling